Читать книгу Harper's New Monthly Magazine, No. XXVI, July 1852, Vol. V - Various - Страница 10

One of the most interesting and curious parts of the process of the manufacture of the barrel, is the straightening of it. We ought, perhaps, rather to say the straightenings, for it is found necessary that the operation should be several times performed. For example, the barrel must be straightened before it is turned, and then, inasmuch as in the process of turning it generally gets more or less sprung, it must be straightened again afterward. In fact, every important operation performed upon the barrel is likely to cause some deflection in it, which requires to be subsequently corrected, so that the process must be repeated several times. The actual work of straightening, that is the mechanical act that is performed, is very simple – consisting as it does of merely striking a blow. The whole difficulty lies in determining when and where the correction is required. In other words, the making straight is very easily and quickly done; the thing attended with difficulty is to find out when and where the work is crooked; for the deflections which it is thus required to remedy, are so extremely slight, that all ordinary modes of examination would fail wholly to detect them; while yet they are sufficiently great to disturb very essentially the range and direction of the ball which should issue from the barrel, affected by them.

The above engraving represents the workman in the act of examining the interior of a barrel with a view to ascertaining whether it be straight. On the floor, in the direction toward which the barrel is pointed, is a small mirror, in which the workman sees, through the tube, a reflection of a certain pane of glass in the window. The pane in question is marked by a diagonal line, which may be seen upon it, in the view, passing from one corner to the other. This diagonal line now is reflected by the mirror into the bore of the barrel, and then it is reflected again to the eye of the observer; for the surface of the iron on the inside of the barrel is left in a most brilliantly polished condition, by the boring and the operations connected therewith. Now the workman, in some mysterious way or other, detects the slightest deviation from straightness in the barrel, by the appearance which this reflection presents to his eye, as he looks through the bore in the manner represented in the drawing. He is always ready to explain very politely to his visitor exactly how this is done, and to allow the lady to look through the tube and see for herself. All that she is able to see, however, in such cases is a very resplendent congeries of concentric rings, forming a spectacle of very dazzling brilliancy, which pleases and delights her, though the mystery of the reflected line generally remains as profound a mystery after the observation as before. This is, in fact, the result which might have been expected, since it is generally found that all demonstrations and explanations relating to the science of optics and light, addressed to the uninitiated, end in plunging them into greater darkness than ever.

The only object which the mirror upon the floor serves, in the operation, is to save the workman from the fatigue of holding up the barrel, which it would be necessary for him to do at each observation, if he were to look at the window pane directly. By having a reflecting surface at the floor he can point the barrel downward, when he wishes to look through it, and this greatly facilitates the manipulation. There is a rest, too, provided for the barrel, to support it while the operator is looking through. He plants the end of the tube in this rest, with a peculiar grace and dexterity, and then, turning it round and round, in order to bring every part of the inner surface to the test of the reflection, he accomplishes the object of his scrutiny in a moment, and then recovering the barrel, he lays it across a sort of anvil which stands by his side, and strikes a gentle blow upon it wherever a correction was found to be required. Thus the operation, though it often seems a very difficult one for the visitor to understand, proves a very easy one for the workman to perform.